Fluorescence in situ hybridization (FISH) is a powerful technology wherein nucleic acids are targeted by fluorescently labeled probes and then visualized via microscopy. FISH is a single-cell assay, making it especially powerful for the detection of rare events that might be otherwise lost in mixed or asynchronous populations of cells. In addition, because FISH is applied to fixed cell or tissue samples, it can reveal the positioning of chromosomes relative to nuclear, cytoplasmic, and even tissue structures, especially when applied in conjunction with immunofluorescent targeting of cellular components. FISH can also be used to visualize RNA, making it possible for researchers to simultaneously assess gene expression, chromosome position, and protein localization.
Signal amplification is of interest for fluorescence in situ hybridization (FISH) to provide visualization of smaller regions of nucleic acids, improve signal to noise/counteract situations of high background, overcome limitations of dim fluorophores, and improve performance for visualizing samples through microscope eye pieces instead of being aided by increased sensitivity of a camera. As such, methods for signal amplification that work for both RNA and DNA FISH are desirable.